1. Field of the Invention
The present invention relates to edge enhancement processing of an electronic camera capable of partially reading out image signals from an image pickup device.
2. Description of the Related Art
There is a known electronic camera which partially reads out any given partial image area from a maximal image area of an image pickup device and performs a series of image processing such as edge enhancement on image signals thereof to generate photographic data on a partial image. For example, Japanese Unexamined Patent Application Publication No. Hei 9-135388 (Paragraph [0187] and FIG. 52) discloses a technique of removing fixed pattern noise caused by a dark current component in an electronic camera capable of partial readout from the image pickup device.
The edge enhancing filter of the electronic camera is set such that an edge of a photographed image is to be optimum at output display on a monitor or a printer. However, in the conventional electronic camera, the same edge enhancing filter is generally used for image data from partial readout (partial image) as well as for image data from all pixel readout, which causes the following problems.
The image data generated in the electronic camera is often enlarged so as to correspond to a predetermined size (for example, in printing, L size, 2L size, or the like) at monitor output and at printing. In such a case, the partial image is enlarged to a size larger than that of the entire image from the all pixel readout. Therefore, the edge width of an edge line of the partial image tends to be wider than that of the entire image.
Moreover, the edge enhancing filter is generally set so that the edge of the image is to be optimum when the entire image is outputted to the monitor or the printer, based on the premise that it is used for the image data on the entire image. When the partial image is outputted in the same size as that of the entire image, therefore, the entire image will be relatively visually desirable whereas the partial image will be visually undesirable due to a high degree of edge enhancement.
Also, the technique in Japanese Unexamined Patent Application Publication No. Hei 9-135388 is for storing in advance data of fixed pattern noise in an area wider than the partial image area in order to prevent a decrease in frame rate when the partial image area is changed, which only prevents re-obtainment of data. Accordingly, Japanese Unexamined Patent Application Publication No. Hei 9-135388 cannot resolve the above-described problems at all.